Traditionally, a camera user loads film into a photographic camera by inserting a film cassette into a film cassette chamber and moving a small portion of film, the film leader, across the film exposing area to a film spool. The camera is then light sealed and ready for operation. After a picture is taken, the camera user then winds the exposed film around the film spool and moves the next frame of film to be exposed into the film exposing area.
Relatively recently a new method of loading film, preloading or prewinding film, has been developed. Film prewinding includes inserting a film cassette into the film cassette compartment and prewinding the film around the film spool on the opposing side of the camera. After a picture is taken, the exposed film is wound back into the film cassette and the next frame of film is moved to the film exposing area. In contrast to the prior method, after the last frame of film is exposed the film is wound back into the film cassette as opposed to around the film spool. Thus, prewinding avoids having to rewind the film back into the film cassette after the pictures have been taken. One advantage of prewinding is that the exposed film is housed within the light tight film cassette and cannot be accidentally exposed by opening the camera.
One problem that has been created by such cameras is that if the camera has a mechanism for rotating the film spindle of a film cassette and a separate mechanism for rotating a film spool, the camera user may operate one of the mechanisms by mistake and move film in the wrong direction. Another problem that has been created with the new method is the possibility that the camera user may accidentally move previously exposed film from the film cassette to the film exposing area and reexpose the exposed film. Still another problem is that the camera user may not properly prewind the film around the film spool. These problems are particularly acute in manual film cameras including “single use” cameras. The camera of this invention has interlocks that prevent moving film in an unwanted direction.
As used herein the term advance or advance direction refers to movement of film out of or away from the film cassette and the term rewind or rewind direction refers to the movement of film into or towards the film cassette.